Information terminal apparatuses, such as cellular telephones and portable information terminals, are now being used. Examples of information terminal apparatuses are so-called smartphones and personal digital assistants (PDAs). An information terminal apparatus executes, for example, an operating system (OS) for controlling user interfaces. Control for user interfaces includes control for displaying screens on a display device and control for outputting sound from a speaker. Under the OS, application programs for performing processing that involves usage of user interfaces, such as a playback operation of moving pictures and sending and receiving of emails, may be executed.
In the field of server computers, a virtualization technology for running a plurality of virtual computers (may also be called virtual machines) on a physical computer (may also be called a physical machine) is now being utilized. A physical machine utilizing a virtualization technology causes each of two or more virtual machines to execute an OS and thereby may execute a plurality of OSs in parallel. A physical machine running a plurality of virtual machines executes control software (may also be called a hypervisor) for allocating resources such as a central processing unit (CPU) and a random access memory (RAM) to the virtual machines.
A computer system of related art sets one of two OSs in the operating state (active state) and the other in the suspended state (inactive state) so that one of the two OSs is exclusively executed. Additionally, a cellular telephone of related art may execute an OS for a personal computer, which is stored in an external apparatus, and upon detecting an incoming telephone call, the cellular telephone stops executing the OS for the personal computer and starts an OS for the cellular telephone.
Japanese Laid-open Patent Publication No. 2008-52714 and Japanese Laid-open Patent Publication No. 2007-129343 disclose related techniques.